International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
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ISSN : 2248-9622, Vol. 4, Issue 5( Version 6), May 2014, pp.33-38
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ARM Soc Based Enotebook
Pranita C Bawankar*, Prof. U. A. Rane**
* M.E.Student, Dept. of Electronics & Telecommunication, S.S.G.M.C.E., Shegaon, India
** Department of Electronics & Telecommunication, S.S.G.M.C.E., Shegaon, India
ABSTRACT
In recent years, electronic media has grown very fast replacing papers, tape devices, books, etc. The new
technologies provide large number of data into single device, fast searching options and more readability than
ever. As eBooks are replacing books; we are proposing ENotebook system in which user can write as he did in
notebook, save, searches and then reread content. This paper presents design and development of ENotebook
using ARM7. The system uses touch screen to get input data and operations like save, delete, open & close of
data file. All data sensed by touch screen is digitized by internal ADCs of LPC2148 microcontroller which gives
low power platform with fast execution. The output is shown on graphical LCD. Whatever user writes on
screen it may need to save for future use. The content of such hand written data will be in graphical/pictorial
form hence required large of memory for storage. We can provide external memory using pen drive, memory
card, EEPROM etc. in this system we are using SD card interfacing through SPI port.
Key Words: ARM7, Graphical LCD LPC 2148, SD Cards ,Touch Screen.
I. INTRODUCTION
Touch screens have been used as an input in
many applications, ranging from ATMs to public
kiosks to travel information desks. But it wasn‘t until
touch screens came in the hands of the public, in the
form of smart phones or music players, did the
thought of it replacing paper came into the mind of
people. The result was smart phones with the
application ‗Touch Notes‘.Touch notes, an
application created by Laboratories For Computer
Nicety Inc., Chicago, Illinois, USA, is a very
common application in all windows, android, and
java phones supporting touch. It allows the user to
scribble, write anything like on paper and to save it.
Also the user can access the previously created pages
and edit them anytime. The popularity of smart
phones, PDAs, portable game consoles and many
types of information appliances is driving the demand
for, and acceptance of, touch screens.Also with time
global warming is an issue about which everyone is
worried. Growing plants is the only solution to this
issue. So to save trees we have to save paper and for
this paperless work is the best solution. Switching to
100% post-consumer recycled paper would more
than triple those impacts, saving over 14,000 trees a
year!! And avoiding over 630 tonnes of greenhouse
gas!
II. LITERATURE SURVEY AND
TECHNOLOGICAL SURVEY
The Pocket PC was a small, portable IBM
PC–compatible computer, introduced in 1989 by
Poqet Computer Corp. with a price of $2000. It was
the first subnotebook form factor IBM-PC-
compatible computer that ran MS-DOS [1]. The
Poqet PC was powered by two AA-size batteries.
Early products included the PenPad 200 handwriting-
only computer terminal, with a digitizing tablet and
electronic pen and no keyboard. With the advent of
the IBM personal computer, later products such as
the PenPad 320 focused particularly on graphics and
CAD/CAM applications for DOS, as well as on data-
entry and data-editing applications.
In early 80s and 90s we get a new platform
called PDA (Personnel Digital Assistant) to have an
option to pcs to carry everywhere. A personal digital
assistant (PDA), also known as a palmtop computer,
or personal data assistant [2], [3], [4] is a mobile
device that functions as a personal information
manager.
With invent of touch technology and
embedded Operating System (OS) a new era begins.
PDAs are largely considered obsolete with the
widespread adoption of smartphones [5]. Nearly all
current PDAs have the ability to connect to the
Internet. A PDA has an electronic visual display,
enabling it to include a web browser. All current
models also have audio capabilities enabling use as a
portable media player, and also enabling most of
them to be used as mobile phones. Most PDAs can
access the Internet, intranets or extranets via Wi-Fi or
Wireless Wide Area Networks.
Apple Computers launched the Apple
Newton stylus based computer in 1993. It utilized
Apple's own new Newton OS, initially running on
hardware manufactured by Motorola and
incorporating an ARM CPU and era of iPhones and
iPads starts [7].After 2007 with the access to
capacitive screens and the success of the iPhone,
multi-touch and other natural user interface features,
RESEARCH ARTICLE OPEN ACCESS
2. Pranita C Bawankar et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 5( Version 6), May 2014, pp.33-38
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as well as flash memory solid state storage and
"instant on" warm-booting; external USB and
Bluetooth keyboards defined tablets. Some have 3G
mobile telephony applications. Most tablets released
since mid-2010 use a version of an ARM processor
for longer battery life. The ARM Cortex family is
powerful enough for tasks such as internet browsing,
light production work and mobile games [8].
Why eNotebook? With above all hand held
devices, the most important factor to select is a cost
for students and researchers. It is cost that matters
and also time to type and capture an image. But, if we
go with e notebook, it will be a great solution to cost
and time. It is developed using an ARM core. So you
can add any feature to system to increase
connectivity, accessibility and storage.
Recently ―Sony‖ introduced a revolutionary
new way to work. Digital Paper from ―Sony‖, in
conjunction with a document management solution,
gives you the power to annotate, share, and save your
documents – all from a handy device that's light
enough to carry anywhere and costing U.S. $
1,100.00 only [9]!
III. OVERVIEW OF SYSTEM
Fig. 1 shows the block diagram for proposed
ENotebook system. The heart of a system is an arm
controller which will get handwritten input from
touch screen and provide it to GLCD to display.
Fig -1: System Block Diagram
As ARM is used instead of using external
signal conditioning and ADC, we will have onchip
ADC. Input captured will be saved on external
memory.
3.1 Touchscreen
3.1.1 Principle of Operation
A resistive touch screen is constructed with
two transparent layers coated with a conductive
material stacked on top of each other. When pressure
is applied by a finger or a stylus on the screen, the top
layer makes contact with the lower layer. When a
voltage is applied across one of the layers, a voltage
divider is created. The coordinates of a touch can be
found by applying a voltage across one layer in the Y
direction and reading the voltage created by the
voltage divider to find the Y coordinate, and then
applying a voltage across the other layer in the X
direction and reading the voltage created by the
voltage divider to find the X coordinate.
3.1.2 Detecting a Touch
To know if the coordinate readings are valid,
there must be a way to detect whether the screen is
being touched or not. This can be done by applying a
positive voltage (VCC) to Y+ through a pull-up
resistor and applying ground to X–. The pull-up
resistor must be significantly larger than the total
resistance of the touch screen, which is usually few
hundred ohms. When there is no touch, Y+ is pulled
up to the positive voltage. When there is a touch, Y+
is pulled down to ground as shown in Fig. 2. This
voltage-level change can be used to generate a pin-
change interrupt [10].
Fig-2: Detecting a touch
3.1.3 Excitation and Measurement Method
The method for measuring the pressure point
is based upon a preferably homogenous resistive
surface (ITO). When applying a voltage to the
electrode pair in the resistive surface a uniform
voltage gradient appears across the surface. A second
ITO layer is necessary to do a high-resistance voltage
measurement. A resistive touch screen can thus be
seen as an electrical switch requiring a small amount
of pressure (0.1 – 1.5 Newton) to close.
Fig-3: Schematic of a 4-wire touch screen when
pressure is applied.
The point of contact divides each layer in a series
resistor network with two resistors (see Fig. 2), and a
connecting resistor between the two layers. By
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measuring the voltage at this point the user gets
information about the position of the contact point
orthogonal to the voltage gradient. To get a complete
set of coordinates, the voltage gradient must be
applied once in vertical and then in horizontal
direction: first a supply voltage must be applied to
one layer and a measurement of the voltage across
the other layer is performed, next the supply is
instead connected to the other layer and the opposite
layer voltage is measured. In stand-by mode one of
the lines are connected to a level triggered interrupt
in order to detect touch activity.
The X and Y coordinates of a touch on a 4-
wire touch screen can be read in two steps. First, Y+
is driven high, Y– is driven to ground, and the
voltage at X+ is measured. The ratio of this measured
voltage to the drive voltage applied is equal to the
ratio of the y coordinate to the height of the touch
screen. The x coordinate can be similarly obtained by
driving X+ high, driving X– to ground, and
measuring the voltage at Y+. The ratio of this
measured voltage to the drive voltage applied is equal
to the ratio of the X coordinate to the width of the
touch screen.
The table below shows connections while
measuring the coordinates.
Table -1:4-Wire Touch Screens Scanning
3.2. The Arm Controller
The analog values received from the
touchscreen are then input to the controller and the
co-ordinates for the touchscreen are calculated and
this in turn acts as an input to the graphic LCD driver
which further drives the LCD to turn the particular
pixel ON.
3.2.1 Advanced Risc Machine (ARM7)
The ARM7TDMI is a member of the
Advanced RISC Machines (ARM) family of general
purpose 32-bit microprocessors, which offer high
performance for very low power consumption and
price [11].
The ARM architecture is based on Reduced
Instruction Set Computer (RISC) principles, and the
instruction set and related decode mechanism are
much simpler than those of micro programmed
Complex Instruction Set Computers. This simplicity
results in a high instruction throughput and
impressive real-time interrupt response from a small
& cost effective chip. Pipelining is employed so that
all parts of the processing and memory systems can
operate continuously. Typically, while one
instruction is being executed, its successor is being
decoded, and a third instruction is being fetched from
memory [11],[13]. The ARM memory interface has
been designed to allow the performance potential to
be realised without incurring high costs in the
memory system. Speed-critical control signals are
pipelined to allow system control functions to be
implemented in standard low-power logic, and these
control signals facilitate the exploitation of the fast
local access modes offered by industry standard
dynamic RAMs. The CPU has two instruction sets,
the ARM and the Thumb instruction set. The
ARM7TDMI is a 3-stage pipeline, 32-bit RISC
processor. The processor architecture is Von
Neumann load/store architecture, which is
characterized by a single data and address bus for
instructions and data. The CPU has two instruction
sets, the ARM and the Thumb instruction set [13].
The ARM instruction set has 32-bit wide
instructions and provides maximum performance.
Thumb instructions are 16-bits wide and give
maximum code density. Instructions operate on 8-,
16-, and 32-bit data types. The CPU has seven
operating modes. Each operating mode has dedicated
banked registers for fast exception handling. The
processor has a total of 37, 32-bit registers, including
6 status registers [11],[12].
3.2.1.1 3- stage Pipeline structure
The pipeline has three stages; FETCH,
DECODE and EXECUTE. The hardware of each
stage is designed to be independent so up to three
instructions can be processed simultaneously. The
pipeline is most effective in speeding up sequential
code [10].
Fig- 4: 3-Stage Pipeline structure
3.2.1.2 Concept of Thumb
The ARM7TDMI processor employs a
unique Architectural strategy known as THUMB,
which makes it ideally suited to high-volume
applications with memory restrictions, or applications
where code density is an issue The key idea behind
THUMB is that of a super reduced instruction set.
Essentially, the ARM7TDMI processor has two
instruction sets:
• The standard 32-bit ARM set
• A 16-bit THUMB set [12]
The THUMB set‘s 16-bit instruction length
allows it to approach twice the density of standard
ARM code while retaining most of the ARM‘s
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performance advantage over a traditional 16-bit
processor using 16-bit registers. This is possible
because THUMB code operates on the same 32- bit
register set as ARM code. THUMB code is able to
provide up to 65% of the code size of ARM, and
160% of the performance of an equivalent ARM
processor connected to a 16-bit memory system [11],
[12].
This allows instruction to be stored in 16 bit
format, expanded into ARM instruction & then
executed. Although the THUMB instruction, they
will achieve a much higher code density. So in order
to build a reasonably sized application that will fit on
a small single chip microcontroller, it is vital to
compile code as a mixture of ARM & THUMB
function. This process is called interworking & is
easily supported on all ARM compilers. By
compiling code in THUMB instruction set we can get
a space saving of 30%, while same code compiled as
ARM code will run 40% faster [11], [13].
Fig- 5: THUMB instruction concept
3.3. Signal Conditioning and ADC
Signal conditioning circuit is used to
amplify the incoming signal from touch screen. Since
output of touch screen is analog, we need to convert
it in digital signal because microcontroller is digital
onchip 10 bit ADC [11], [12], [13].
3.4. Graphical LCD
Graphical LCD contains Dot matrix for
display. To store the ON / OFF values of this dot
matrix requires large memory and also it needs to
refresh content of LCD screen after a particular
interval. Since microcontroller might busy in to the
other stuffs like sampling, processing, and saving,
retrieving data from memory hence LCD driver is
required which does all these operations [15].
Figure 6: Graphical LCD
3.5. External Memory
Whatever user writes on screen it may need
to save for future, using pen drive, memory card,
EEPROM etc. Content of such hand written data will
be in graphical / pictorial form hence requires large
memory for storage. We can provide external
memory as well. Here in this system SD card is used
as external memory and interfaced using SPI protocol
[14][16][17].
Fig- 7: SD card and reader.
3.6. Power Supply
The system required different power supply
as follows;
3.3V for ARM microcontroller.
5V for signal conditioning circuit and graphical
LCD [11], [13].
3.7. Flow of working
Graphic LCD and Touchscreen are
initialized when we switch on the Digital Paper.
Then, a welcome message on LCD is displayed once
the device is ON and then it checks for the presence
of a memory card, then a message is shown
accordingly if card is successfully detected or not.
Once the device is successfully initialized we can do
calibration of the touchscreen by selecting proper co-
ordinates through the touch input and by checking if
touch input for calibration is within specified limits
or not, then a message is displayed accordingly. Once
calibration is done successfully, the menu page is
shown which consists of four options namely
WRITE, OPEN, SAVE and CLEAR. We can select
one of these tasks to perform an operation. The
controller detects continuously for a valid touch, and
if detected, checks the pixel touched is in the blank
space or if it is inside the menu block. If touch is in
blank space, then the corresponding co-ordinates
generate a voltage which is transmitted to the
controller to perform the operation on the LCD.
Depending on the actual values of touch point the
corresponding pixels are lit on LCD (as our LCD is
placed right below the touchscreen). It shows four
pixels for a touch detected at one point, so the drawn
line is thick enough to be visible.
Now if one of the MENU options is
selected, then the corresponding operations are
performed.
If OPEN – it opens all files in the memory
card, shows cancel option in menu, and keeps on
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detecting for a touch to select a file, or the cancel
option. If cancel is selected go to starting screen,
else if a file name is selected, it opens the
corresponding file. Nothing happens if any clear
part of the screen is touched.If SAVE – then it
saves the current display as a new file.
If CLEAR – then it clears the complete
drawing portion, refreshes LCD and displays
menu again
WRITE/ERASE – initially when the screen
is touched, the corresponding pixels are lit up, and
Erase option is available on the menu. On
selecting the ‘Erase‘ option, the touching of
screen will erase the corresponding pixels on the
screen, and in place of the erase option, ‗Write‘
option is displayed. This can be clicked and used
to return to write mode.
IV. SOFTWARE DESIGN
4.1 Flowchart
The software platforms used for completion
of tasks in flowchart are as follows-
4.2 Keil μVision4
μVision is a window-based software
development platform that combines a robust and
modern editor with a project manager and make
facility tool. It integrates all the tools needed to
develop embedded applications including a C/C++
compiler, macro assembler, linker/locator, and aHEX
file generator. μVision helps expedite the
development process of embedded applications by
providing the Integrated Development Environment.
KEIL can be used to create source files;
automatically compile, link and covert using options
set with an easy to use user interface and finally
simulate or perform debugging on the hardware with
access to C variables and memory. Unless you have
to use the tolls on the command line, the choice is
clear. KEIL Greatly simplifies the process of creating
and testing an embedded application [19].
4.3 Flash Program Utility
For downloading the application program
into FlashROM, this utility tool is necessary. The
program code generated in C language after
processing produces object code in hex form. It is
referred as .hex file. To dump this hex code in the
flash ROM of the controller the facility is provided
with Keil version 4. For programming with older
versions, the same task is completed with the help of
software called Flash Magic [20].
V. RESULT
Fig.8, 9, 10, shows images of ENotebook
screen implemented using this paper concept. Fig 8
shows the 1st screen when power is on. In fig 9
shows all the menus are initialised. When we are
writing or drawing at that time ERASE menu is
displayed this means by default it is WRITE menu.
But when we are erasing whatever we have written
then WRITE menu get initialised on screen as fig10.
Fig. 8- Initializing Screen
Fig. 9- Showing All Menus
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Fig. 10: erasing an image
VI. CONCLUSION
The system prescribed here is the one with
Touch screen interface which made it more
interactive to user. Data drawn on touch screen is
displayed on LCD and saved on SD card. The file
stored is only of BMP monochrome format. Memory
expansion is also possible. It provides a User friendly
GUI User can store data in one‘s own handwriting.
We can connect such systems together using wi-fi or
any other communication protocol and can share
data. Most importantly the data can be retrieved any
time especially for researchers, students it makes
their work paperless and saves paper
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